Here's why:
* Safety: Adding fluid to a running transmission can create a dangerous situation. The hot fluid can spray out, causing burns.
* Accuracy: It's difficult to accurately check the fluid level when the engine is running. The fluid will be churning, making it hard to get a clear reading on the dipstick.
* Overfilling: Overfilling the transmission can cause damage to the internal components.
Here's the proper procedure for checking and adding transmission fluid:
1. Park on a level surface.
2. Warm up the engine and transmission by driving for a few minutes. This will ensure the fluid is at the correct temperature for an accurate reading.
3. Shift the transmission through all gears (P, R, N, D, 1, 2, 3) and back to "Park."
4. Wait a few minutes for the fluid to settle.
5. Remove the dipstick and wipe it clean.
6. Reinsert the dipstick all the way and remove it again.
7. Check the fluid level against the markings on the dipstick.
8. If the fluid level is low, add transmission fluid as needed.
9. Re-check the fluid level after adding fluid.
Important: Always consult your owner's manual for the specific instructions and recommendations for your 1994 Isuzu Trooper.
It's always best to have a qualified mechanic perform transmission fluid checks and services.
